1997 SSEi, Just bought car. Started with the basics, changed all filters and fluids. Began performance tuning. Installed Autolite Dual Platnium APP605 @ .055, improvement over stock. Next installed a set of Magnecor 8.5mm wires, again an improvement. Installed an Intense Std PCM and 180 stat, what an improvement. I then installed Gatorback belts on the accessory drive and the */C drive, eliminated slippage. Great so far and I felt this was a good order of progesssion. I then decided to work on the air intake, I am working on a couple of CAI designs but for now I decided to put a K&N stock replacement air filter in. As soon as I started the engine I could hear the difference in the air being sucked in. I hen took the car for a test drive an you could feel the difference, throttle response and power. After approx 25 miles when I come to a stop with the car in gear I feel a rough idle, when in park you see the engine shake a bit and the throttle response has fallen off a bit. Any ideas? Possible contamination of MAF or IAC? Checked for the obvious, loose connections, plug wires.

First off, you dont want to run plantinum plugs on a supercharged car. I use the coper plugs. I think its because platinum has a lower melting point. IM not sure if thats whats causing your problems or not though.

It is quite possible that your K&N air filter was over-oiled out of the box. If this oil gets on to the MAF (mass air flow) sensor, it can cause these problems and some others if left unattended. I had the same issues with my '01 SSEi after installing a K&N panel filter. It is very easy to over oil the filter when you clean it, but my problem was also due to the filter being over oiled out of the box. I have done one cleaning since on my filter and after the cleaning I sucked the living crap out of the filter with my shop vac. No problems since.

+1

Did you remove or ding your MAF screen? Do you have a scanner? With a scanner you can check your IAC counts which should be between 50-80 if they are low could be a vaccum leak. You can get special electrical cleaner to try and clean the MAF itself or you can just unplug it while the car is idling and see if it smooths out (bad MAF).

I did not damage the screen, I hope to get my hands on a scanner this week.

Blanket statement... Plenty of SC cars use plats, the 3.8SC by Ford damn near requires them. However there are none that work with the L67 with any success (that anyone'* mentioned yet). If you can pinch for it, Denso is #1 hands down, however NGK or autolite will not let you down at all.

hmmmmm makes me wonder...

i got new platinums on my car last summer (as soon as i installed them i came here and you guys said to use copper ), and now i got laggy throttle response and kinda poor mileage. do you think the spark plugs are worn out from not using copper plugs? would that show the symptoms im having?

Platinum plugs do not wear as easy as copper. They last a lot longer which is why they are so popular. However they DO hold heat more than copper and thus raise cylinder temps and can lead to KR. This is why most dont run them in modded SC engines.